🇰🇷 한글 설명
Linux 커널의 ip6_tunnel 구성 요소에서 __ip6_tnl_rcv() 함수가 초기화되지 않은 데이터를 참조할 수 있는 취약점이 발견되었습니다. 이는 IPv6 터널링 패킷 처리 과정에서 헤더 데이터를 올바르게 검증하거나 초기화하지 않아 발생하며, KMSAN(Kernel Memory Sanitizer)에 의해 탐지되었습니다.
💡 쉬운 설명
네트워크 패킷을 처리할 때 컴퓨터 메모리의 빈 공간(초기화되지 않은 값)을 잘못 읽어 들여 시스템 오류를 일으킬 수 있는 문제입니다. 이로 인해 시스템이 불안정해지거나 보안 문제가 발생할 수 있습니다.
🇺🇸 원문 (English)
In the Linux kernel, the following vulnerability has been resolved:
ip6_tunnel: make sure to pull inner header in __ip6_tnl_rcv()
syzbot found __ip6_tnl_rcv() could access unitiliazed data [1].
Call pskb_inet_may_pull() to fix this, and initialize ipv6h
variable after this call as it can change skb->head.
[1]
BUG: KMSAN: uninit-value in __INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline]
BUG: KMSAN: uninit-value in INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline]
BUG: KMSAN: uninit-value in IP6_ECN_decapsulate+0x7df/0x1e50 include/net/inet_ecn.h:321
__INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline]
INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline]
IP6_ECN_decapsulate+0x7df/0x1e50 include/net/inet_ecn.h:321
ip6ip6_dscp_ecn_decapsulate+0x178/0x1b0 net/ipv6/ip6_tunnel.c:727
__ip6_tnl_rcv+0xd4e/0x1590 net/ipv6/ip6_tunnel.c:845
ip6_tnl_rcv+0xce/0x100 net/ipv6/ip6_tunnel.c:888
gre_rcv+0x143f/0x1870
ip6_protocol_deliver_rcu+0xda6/0x2a60 net/ipv6/ip6_input.c:438
ip6_input_finish net/ipv6/ip6_input.c:483 [inline]
NF_HOOK include/linux/netfilter.h:314 [inline]
ip6_input+0x15d/0x430 net/ipv6/ip6_input.c:492
ip6_mc_input+0xa7e/0xc80 net/ipv6/ip6_input.c:586
dst_input include/net/dst.h:461 [inline]
ip6_rcv_finish+0x5db/0x870 net/ipv6/ip6_input.c:79
NF_HOOK include/linux/netfilter.h:314 [inline]
ipv6_rcv+0xda/0x390 net/ipv6/ip6_input.c:310
__netif_receive_skb_one_core net/core/dev.c:5532 [inline]
__netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5646
netif_receive_skb_internal net/core/dev.c:5732 [inline]
netif_receive_skb+0x58/0x660 net/core/dev.c:5791
tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1555
tun_get_user+0x53af/0x66d0 drivers/net/tun.c:2002
tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:2084 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0x786/0x1200 fs/read_write.c:590
ksys_write+0x20f/0x4c0 fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__x64_sys_write+0x93/0xd0 fs/read_write.c:652
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b
Uninit was created at:
slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
slab_alloc_node mm/slub.c:3478 [inline]
kmem_cache_alloc_node+0x5e9/0xb10 mm/slub.c:3523
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560
__alloc_skb+0x318/0x740 net/core/skbuff.c:651
alloc_skb include/linux/skbuff.h:1286 [inline]
alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6334
sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2787
tun_alloc_skb drivers/net/tun.c:1531 [inline]
tun_get_user+0x1e8a/0x66d0 drivers/net/tun.c:1846
tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:2084 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0x786/0x1200 fs/read_write.c:590
ksys_write+0x20f/0x4c0 fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__x64_sys_write+0x93/0xd0 fs/read_write.c:652
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b
CPU: 0 PID: 5034 Comm: syz-executor331 Not tainted 6.7.0-syzkaller-00562-g9f8413c4a66f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
📍 영향받는 시스템
Linux kernel versions prior to the fix (specifically affecting ip6_tunnel module)
⚔️ 공격 벡터
조작된 IPv6 터널링 패킷을 전송하여 커널의 uninitialized memory access 유도
🛡️ 대응 방법
Linux 커널을 최신 보안 패치가 적용된 버전으로 업데이트하여 pskb_inet_may_pull() 호출 및 변수 초기화 로직 적용
🔧 검증 코드
출력된 커널 버전이 취약점이 해결된 패치 버전 이후인지 확인하십시오.